1. Technical Field
The invention relates generally to a chair. More particularly, the invention relates to a chair having a three-piece back which flexes to wrap around and cradle an occupant's back. Specifically, the invention relates to a chair having a generally L-shaped seat member with a vertical section which forms a base of the back, and right and left back portions hingedly connected to the vertical section of the seat member and to each other.
2. Background Information
A number of chairs have been ergonomically designed to fit the human body. These chairs are designed to support the occupant's spine in an optimum fashion. Some of these chairs involve a complex and correspondingly expensive mechanism. Additionally, adjusting these chairs can be complicated, with the result that the advantages they offer cannot be fully utilized. Many chairs are also fitted with superfluous parts making the chair heavy and expensive. A chair designed in accordance with ergonomic principles should be capable of adapting to the movements and the anatomy of the human body so that the occupant can work at optimum efficiency over long periods.
Thus, difficulties of the kind outlined above have a negative, rather than a positive, effect. A correctly designed chair seat embraces and supports the body up to the pelvis in order to allow the trunk to move as freely as possible. When the occupant of the chair remains seated for a prolonged period of time, the natural position of the spine should be maintained.
Additionally, an ergonomically designed chair should support the user's back when in a seated position while simultaneously providing sufficient flexibility to allow the user to move from a seated position to a partially supine position. As the user moves from a seated position to a partially supine position, the chair should permit sufficient flexibility so as to not apply undue force to the user's back, while flexibly receiving the user's back. While the prior art is presumably adequate for the purpose for which it was intended, it does adequately support the user as the user moves from a seated position to a partially reclined position.
Additionally, seats of this type are often used in an office environment where the user is often required to rotate one arm to a position behind the chair such that the back rotates at least partially from a forward to a rearward position. In so doing, the back often provides a rigid surface against which the back must rotate. Again, while prior art devices are presumably adequate for the purpose for which they are intended, they do not provide adequate flexibility when a user applies force against one side of the chair rear support, for example, when the user stretches or rotates to move one hand to a location behind the chair.
Examples of chairs which support an occupant's back and spine are shown in U.S. Pat. No. 4,007,962 which discloses a chair with an adjustable back. The chair includes a central section hingedly attached to the rear of the seat, as well as an upper portion flexibly mounted to the top of the center section and extending around both sides thereof.
U.S. Pat. No. 4,157,203 discloses an articulated double back for chairs. The device provides an upper and lower section having a flexible hinge extending intermediate the upper and lower section to provide independent movement therebetween.
U.S. Pat. No. 4,585,272 discloses a chair having a back having a plurality of articulated segments. The chair has a reclineable backrest formed by a series of at least three superimposed segments attached together about respective horizontal axes. The device is moveable to correspond to the arched back of the occupant.
U.S. Pat. No. 4,830,430 discloses a chair having a pair of springs formed of two U-bent spring rods which couple a lower back portion of the chair to an upper back portion of the chair. The effective spring length of the springs is adjustable or changeable by moving a slider connected to one of the back portions.
U.S. Pat. No. 5,195,804 discloses a backrest having two oval-shaped shells each concave to vertical and convex to horizontal. The backrest includes two backrest shells arranged side by side.
U.S. Pat. No. 5,249,839 discloses a chair with independent control of a lumbar portion of a seat back and a thoracic portion of the seat back. The chair has a seat connected to a base and a control connected to the base under the seat.
Although these prior art devices are adequate for the purpose for which they are intended, some of these chairs include backs which merely pivot toward and away from the seat member allowing the occupant to recline in the forward and backward direction. These chairs fail to disclose a split back having separate right and left portions hingedly interconnected to assure that movement of one of the right and left portions cause movement of the other of the right and left portions through a flexible interconnection. Other of these prior art chairs disclose a split back chair which requires highly mechanical components which facilitate a right and left flexing movement. These chairs are heavy and tend to be expensive to purchase due to the large number of parts associated with the chair.
Therefore, the need exists for a chair which has a simplified design and which includes a generally L-shaped seat member and separate right and left back portions hingedly interconnected and hingedly connected to the seat member. The need also exists for a chair which permits one back portion to move relative to the other when forces applied to the back at a single adjacent one side thereof.